This invention relates generally to the transport, introduction, atomization, and excitation of the constituents of elevated temperature sample streams whose chemical compositions are to be determined by spectrometric techniques; more specifically, to the transport, introduction, atomization, and excitation of the emission spectra of the constituents of elevated temperature sample streams whose sodium and potassium concentrations are to be determined and monitored continuously by flame emission spectrometric techniques.
In energy generation schemes in which hot gas product streams derived from the combustion or gasification of coal are ultimately used to drive turbine-generator assemblies, determination and continuous monitoring of the concentrations of sodium and potassium that are present in the gas streams is important for characterization and monitoring of the performance of hot gas cleanup equipment and processes. Minimization of turbine corrosion is one of the principal goals of the hot gas cleanup operation. The important concentrations are: vapor-borne sodium, particulate-borne sodium, vapor-borne potassium, and particulate-borne potassium. The concentrations of importance are those which prevail at actual process operating temperatures and pressures.
Flame spectrometric methods have been shown to have sufficient detecting power, accuracy, and precision for such determinations and, when combined with appropriate means for continuous introduction of a representative sample of a gas stream of interest, can provide continuous concentration monitoring. For accuracy, avoidance of the loss of alkalicontaining materials by condensation of vapor prior to introduction of the sample stream into the atomization/excitation cell is a critical requirement.
It can therefore be seen that, particularly where there is use of gas turbines in systems fueled by coal or coal derived fuels, there is a continuing need for monitoring alkali-containing materials, particularly. The process stream portions that are of primary interest with respect to alkali monitoring are (1) the turbine input gas stream for characterization of the alkali portion of the corrosive atmosphere to which the turbine components will be exposed, and (2) the inputs and outputs of hot gas cleanup devices for determination and online monitoring of the efficiency of trial systems.
This invention has as a primary objective the development of a method and apparatus for excitation of the emission spectrum of a flowing representative sample of hot gas, with continuous monitoring of the spectrum to be employed for online determination of sodium and potassium concentrations in gaseous fuels produced from coal and in hot flue gas from combustion of coal and/or other fuels produced from coal.
Another object of the invention is to provide an apparatus which utilizes the momentum of an elevated temperature sample stream exiting from a heat traced and thermally insulated sample transport/sample introduction tube for introduction of vapor and (liquid and/or solid) particulate constituents of the sample stream, without temperature degradation, into the axial channel of a flame atomization/excitation cell for subsequent analysis of the materials present in the sample stream by spectrometric methods.
A still further object of the invention is to provide an apparatus which employs heat tracing and appropriate thermal insulation materials with the sample transport/sample introduction tube so that vapor state material which enters that tube remains in the vapor state during its transit of the tube and enters the axial channel of the flame atomization/excitation cell as vapor state material.
A yet further object of the invention is to provide an apparatus which produces a flame atomization/excitation cell in a manner that provides superior accessibility for the introduction of material into the axial channel of the flame atomization/excitation cell.
Another object of the invention is to provide an apparatus which produces a flame atomization/excitation cell with a high degree of accessibility for the direct introduction of material into the axial channel of the flame atomization/excitation cell, and sufficient working space immediately below the flame atomization/excitation cell to allow the generation of vapor, liquid, or aerosol streams from solids, liquids, solutions, slurries, powders, or corrosive materials and direct introduction of such streams into the axial channel of the flame atomization/excitation cell.